Method and apparatus for determining the location of water strata in wells



G. H. ENNIS Dec. 23, 1930.

METHOD AND APPARATUS FOR DETERMINING THE LOCATION OF WATER STRATA INWELLS 2 Sheets-Sheet l Original Filed Jan. 9, 1926 NOR/VIAL FLUID LEVELCoA/NA rf o/L SAND wArfR smv@-P Dec. 23, 1930. G. H. ENNls 1,786,195

METHOD AND APPARATUS FOR DETERMINING THE LOCATION OF WATER STRATA INWELLS Original Filed Jan. 9, 1926 2 Sheets-Sheet 2 CON/YA Y! I N VEN TOR. G50/Q65 H. Mv/s A TTORNE Y.

Patented' Dec. z3, 1930 GEORGE H. ENNIS, 0F LONG ,PATENT oFFlcE d BEACH,CALIFRNIA, .ASSNOR 0I' ONE-HALF T0 ROBERT V. FUNK, OF ANAHEIM,CALIFORNIA x nnTnon AND APPARATUS non DTEBNINING THE LOCATION or WATERsTnATA rrry WELLS Application led January 9, 1926, Serial No. 80,160.Renewed December 28, 1929.

This invention relates to method and apparatus for determining. thelocation of water strata in wells.

The general object of the invention is to provide an improved method andapparatus whereby the location of the strata of water in the well can beaccurately determined.

The method in common use for locating 'water strata in oil wellsincludes washing the well by inserting a tubing in the well and passingfresh water downward through the tubing into the lower portion of theWell. When the overflow from the top of the well-is found to be fresh,the washing is stopped and the tubing withdrawn. A pair of spacedelectrodes is then lowered to the bottom of the well and raised again, auniform potential of electric current being imposed .upon theseelectrodes. During the lowering and raising of the electrodes, theresistance of the water to the passage of the current between theelectrodes is recorded by a Wheatstone bridge. If this resistance showsa marked 'variation at any depth in the well, it is known that connatewater is still present in the well at this depth and after theelectrodes have been withdrawn, the tubing must be again lowered to apoint near the bottom of the well and the y washing continued.

This washingl must be repeatedV until the resistance of the waterisfound practically uniform at all points in the well. The level ofliquid in the well is then lowered by bailing until somewhat belownormal level. This ter.

causes connate water to iow into the fresh water in the well from thewater strata which communicate with the well. Connate water is almostinvariably saline and therefore a better electrical conductor than thefresh wa- The electro-des are now lowered through the well and the.resistance to flow of current between the electrodes recorded atvarious depths in the well. Wherever the connate water is entering thewell, the resistance will decrease greatly and this will be indicated onthe record graph by a distinct peak.

Many difficulties are met with in carrying out the above `outlinedmethod, not the least of which ,is the necessity of repeatedlylowel-ling and raising a string of tubing practically throughout the length ofthe well.

It is an object of my invention to provide a method for the location ofwater strata in oil wellsin which the lowering of tubing into the wellfor displacing the contents 'of the well with .another liquid isunnecessary.

In thus displacing the liquid in the well by another liquid, itisnecessary that the lower end of the tubing be disposed Several hundredfeet above the bottom of the well in order to prevent the tubin beingsanded up or embedded in sand p aced in circulation by the force of thejet of liquid leaving the tube. Thus, the liquid in the well below thelower end of the tube is not materially affected by the washing processso that any resistance recorded when the electrodes are in this extremebottom 'portion of the well is practically meaningless as far asindicating the location of water strata is concerned.

It is another object of my invention to provide a method for thelocation of water strata in oil wells in which water strata may beaccuratel located in the extreme lower part of a well 1n the sameoperation in which water strata opening into the remainder of the wellare located.

In different -wells the salinity of the connate waters varies instrength so that when the variation in resistances between one liquidand the connate waters is relied upon to record the 'locations of waterstrata, this y record often wrongly indicates the relative iiows fromlvarious Strata.

It is a still further object of my invention to provide a method for thelocation of water strata in oil wells in which the degree of salinity ofthe connate waters is practically` a negligible factor in determiningthe character of the record. Y

In the old process referred to above, practically the entire well mustbe treated or at least all of the well forfa given distance down fromthe upper end thereof.

It is an object of my invention to provide a method for the location ofwater strata in oil wells in which a given zone may be tested exclusiveof the remainder of the well.

Yet another object of my invention is to provide a novel apparatus forcarrying out the method of my invention.

Another object of the invention is to provide an improved constructionof elements for use with water locating'apparatus.

A further object of the invention is to provide a novel means forrecording variations in potential difference between elements which aresuspended at varying depths in wells.

Other objects of the invention will be apparent from the followingdescription taken in connection with the accompanying draw in s,wherein:

ig. 1 is a diagrammatic section of an oil well showing a chemicalcartridge being lowered therein;

Fig. 2 is a view similar to Fig. 1 showing a bailer in operation;

Fig. 3 is a similar view showing elements being lowered therein;

Fig. 4 is an elevation 'of the element or plate assembly;

Fig. 5 is a view similar to Fig. 4 with the top portion in section;

Fig. 6 is a cross section taken on line 6-6 of Fig. 4;

Fig. 7 is a diagrammatic view showing a wiring diagram and associateparts, and

Fig. 8 is a view of a chart made with my device.

In the following description I will describe my method and apparatus asused in connection with oil wells where it is of particular use indetermining the 'location ofy water bearing strata. In order that an oilwell may produce a good grade of crude oil, it is necessary that thewater be cemented oli'. To do this, it is first necessary that the waterstrata be located before the water may be excluded from the well.

Referring to the drawing by reference characters, I have shown an oilwell generally at 10. I This wellis shown as provided with a casing 11which may be suitably anchored in the casing head 12. Another casing isshown at 14 and this case supports, at its lower end, a string ofperforated casings 15.

The normal fluidlevel is indicated at 16 while the connate oil sands areindicated at 17. A gas sand is shown at 18 and a connate water strata isindicated at 19. The

roblemwhich my invention solves is the ocating of this last mentionedstrat-um 19 which bears the objectionable water.

In carrying out m' invention I may arrange a frame 20 adjacent thecasing head 12. Upon this frame I mount a cable drum 21. which may beoperated in any desired manner. A

, In the preferred practice of my invention I employ a cartridge-likecasing 24, the sides of which are made of reticulated mesh. This casingis adaptedto be lowered in the Well.

It' is first lled with a suitable material, which when dissolved in thefluid in the Well, will form an electrolyte. I have found reel (notshown) and by means of the bailer I lower the normal fluid level adesired amount to cause connate oil and connate water to enter the well.

My testing apparatus also includes an elemental device 25. Thiselemental device is suspended by a cable 26 which includes two leads 27and 28. The cable 26 has one end fastened to the cable drum 21previously described and has the other end fastened to the elementaldevice 25.

This elemental device includes a top portion 29 having a bail 30 thereonto which the cable 26 is secured by means of a clamp 31. This clamp 31may engage a compression member 32 although the specific details ofsecuring the cable to the elemental device may vary.

The elemental device also includes a bottom portion 33 on which a weight34 is arranged. The top portion 29 and the bottom portion` 33 areprovided with insulating members 35 and through these insulated membersa central insulating rod 36 extends.

, About the rod 36 I arrange, preferably in a helicalform, a pair ofspaced elements 37 and 38. One of the elements, for instance 37, may bemade of zinc While the other element 38 may be made of copper. In lieuof these elements others may be used so long as they will possess thenecessary characteristics. The elements are shown as connected at theirupper ends to the leads 27 and 28 as shown at 39 and 40 in Fig. 5.

The elements are spaced apart suitable distances and are insulated fromeach other so that variations in potential difference will exist betweenthe two elements when they are lowered in the electrolyte by unrollingthe cable 26. f l

The elemental member 25 is provided with l guard members 41 to preventinjury to the elements and with vanes 42 at the top and bottom. Thesevanes 42. are arranged in a direction reverse to the direction of theelements 37 and 38 so that the members will counteract each other, thuspreventing rotation of the elemental member while it is being lowered inthe well. The curvature of the elements causes them to keep clean inuse.

The cable 26 passes over a pair of idlers 44 and over a drum 45 so thatas the cable is unwound and wound when it is lowered in the well andlifted in the well, the drum will be turned by the friction of thecable.

This drum 45 is connected by means of'aflexible shaft 46 with a shaft 47on which a. pair of beveled gears 48 and 49 are connected for slidingaction. Eithei` one of these gears is adapted to be thrown intoengagement with a beveled gear 50 by actuating a pivoted rocking arm 51.The gear 50 is mounted on the shaft 51 of a paper supporting drum 52.From the foregoing description it will be apparent that continuousmovement of the paper 52 in the same direction may be effected byshifting the lever 51 when the direction of the movement of the cable 26is changed.

The leads 27 and 28 in the cable 26 pass from the drum 21 throughcontacts thereon to wires shown in a wiring diagram in Fig. 7. The lead27 is in circuit with a terminal 51b of a pole changing, four Way switch51c as shown in Fig. 7.

The lead 28 is in circuit with a contact 52a of the pole changing switch51, previously mentioned. The other two terminals of the switch areshown at 58 and 54 in Fig. 7. The terminal 54 is connected by means of alead 55 with a lead 56 which is in turn connected to a terminal on arecording voltmeter 57. This voltmeter has an indicating pointer orindi` cator arm 58 which is provided with suitable marking materialthereon so that it will mark on the paper arranged on the drum 52previously described. p

The terminal 58 is connected by a lead 60 with a rheostat 61, Therheostat is connected to a battery 62. This battery 62 is connected toanother rheostat 63 which is also connected to the lead 56. The rheostatis connected by a lead 64 to a battery 65 whence a lead 66 passes to theother terminal 69 of the voltmeter.

The lead 68 is connected with the lead 60 by means of a lead 70 and theconstruction y of parts is such that by shiftingv the rheostat controlsthe ,voltage produced by the batteries may be made to correspond to thepotential differences across the elements of the elemental members 25 sothat the indicator needle 58 may be made to read zero. l

A sheet of paper adapted foruse with my invention is shown at 75. Thispaper is ruled with transverse lines 76 to indicate depth. The paper isalso ruled with longitudlnal lines as at 7 7 to provide an arbitrarymarking for indicating variations'in potential differ' ence. The papermay be mounted on the drum 52 in any desired manner.

In using my apparatus the fluid level is i determined by lowering theelemental member 25 in the well. The point at which the elements areimmersed in the fluid will be indicated by the needle 58. The rheostatcontrols are then moved so that the E. M. F. of the batteries 62 and 65and the elemental well.

member 25 are balanced thereby causing the needle 58 to assume aposition at the zero mark as shown at 80 in Fig.' 8.-

The drum 21 is then operated and the elemental memberlowered to thebottom of the The member 51 is then reversed and the cable is withdrawn.The operation of the gears causes the paper roll to revolve in the samedirection so that a graph is made as the elements go up and down. If thewell has been properly washed the needle 58 will assume a position atzero or nearly so, which would show the fluid to be substantially thesame throughout the depth of the well.

The next step is to lower the cartridge-like casing 24 filled withammonium chloride or other suitable material into the well therebymaking an electrolyte. The elemental member 25 is then again loweredinto the well. As soon as the elements are immersed in the electrolyte,the batteries and elements are again balanced and then lowered to thebottom and returned as before. If the charge of electrolyte has beencomplete the needle 58 will assume a position at zero or nearly so,during this operation. If charge is not complete a curve on the chartwill show the exact depth that the electrolyte is weak. The cartridgecasing 24 is then lowered to the zone or zones indicated as weak on thechart, and raised and lowered in that zone until the fluid is changed.The elements are then again lowered, and this process is repeated untilthe reading on the chart is zero or nearly so. v

Next the electrolyteis lowered below the fluid level by bailing. Theamount should be just enough yto start the'formation fluids entering thewell. Another run of the elemental member 25 is then made. The fluidentering the well from the various strata will be indicated by thechange in the electrolyte opposite the oil zones and formationscontaining water. This will throw the instrument out of balance causingthe needle 58 to register a curve 81 on the chart to the right or leftof zero depending onthe chemical action of the electrolyte on theelements. After the elemental member has been lowered some distance, itmay enter the water bearing areas so that the varying potential we-lland the member 51 has bcn reversed, the

next graph will make a curve 84 which will correspond approximately withthe curve 82. Several subsequent runs of the elements will be made, thefluid level being lowered each time by hailing prior to each run.Calcula tions based. on the peak of the curves 82 and 84 will thenindicate the exact point 4of en- Cil trance of the water so that it canbe cemented ofi".

If the electrolyte becomes diffused with salt Water more chemical can belowered in the well to strengthen the electrolyte.

The renewal of the electrolytic solution is thus seen to be a verysimple and inexpensive operation quickly accomplished'by the lowering ofthe chemical cartridge 24 in'to the area where the electrolyte has beendiluted, and raising and lowering this cartridge until the electrolyticsolution is restored. In order to check the uniformity of theelectrolytic solution at any time, the cartridge 24 need merely bewithdrawn from the well on its cable and the elemental device 25 loweredfor a test record. This requires only a small fraction of the timerequired in the old process for lowering and raising a tube from thebottom of a well several thousand feet deep in the washing of the well.In the old process thirty-six hours is usually consumed in merelycompleting the washing step, while. in the extensive use of my process,I have uniformly completed the entire survey of the well in from twelveto twenty-four hours.

It is desired to point out that the submerging of the copper and zincIelectrodes 37 and 38 in the solution of ammonia chloride forms avoltaic or galvanic cell which chemically sets up a difference ofpotential between these electrodes. The variation in this potential isthe basis of the testing of the strength of the solution and this isparticularly desirable as it is practically independent of the salinecontent of the well water.

Having thus described my invention, I claim: c

A 1. The method of locating water bearing strata in a well, comprising:dissolving an ionizable chemical in the water in said well; loweringplates into said solution of a character to form a voltaic cell whendisposed in said solution; moving said plates through said solutionwhile held in spaced relation;

and recording the potential difference between said plates during saidmovement.

2. The method of locating water bearing strata in a well, comprising:dissolving an ionizable'chemical in the water in said well havingdifferent electro-chemical qualities from that possessed by a principalsolute already in said water to form a uniform solution of said chemicalin a given zone of said well lowering the pressure of said solution insaid well; and testing the liquid at various points in said zone todetermine the degree to which said electro-chemical qualities arepresent in said liquid.

3. The method of locating water bearing strata in a well, comprising:lowering a relatively concentrated ionizable chemical into a well toform a practically uniform solution in the water already in said well;reducing the hydrostatic head of said solution on said well; allowingthe well to rell substantially to its former level by the naturalingress of lwater; and electrochemically testing said points -todetermine where y Water flowing into the 'strata in a well, comprising:lowering a relatively concentrated ionizable chemicalinto a column ofwater in a well; mixing said chemical with said water in al zone of saidcolumn to form a relatively uniform electrolytic solution of saidchemical in said zone; reducing the pressure of said solution on saidwell; and electrochemically testing said solution at various pointsftodetermine where it has been diluted by connate fluid flowing into thewell.

5. The method of locating water bearing strata in a well, comprising:lowering an ionizable chemical into a column of water in a well; mixingsaid chemical with the water in a zone of said column to form apractically uniform solution of said chemical in said zone; loweringplates into said solution of a character to form a voltaic cell whendisposed in said solution; moving said plates through said solutionwhile held in spaced relation; and recording the potential differencebetween said plates during said movement.

6. In an apparatus of the class described: a pair of dissimilarelectrode elements adapted to be freely moved within a well; a pair ofleads connected to said elements and adapted to extend to the top of awell; an electro potential producing means capable of functioning at thetop of said well to produce a variable potential dillerence which may bemade to balance the potential difference generated between the saiddissimilar metallic elements; and an indicating means electricallyconnected to said leads and said potential producing means and capableof registering as a function of the dilerence in potential existingbetween said leads and said potential producing means.

7. A method of testing a well to determine the location of any strata atwhich a fluid enters said well, said method including the steps of:providing said well with a body of electrolyte; lowering electrodes intosaid electrolyte, of a character to form a voltaic cell when disposed insaid electrolyte; moving said electrodes through said electrolyte whileheld in -spaced relation; and measuring the potential dierence betweensaidelectrodes.

8. A method of testing a well to determine the location of any strata atwhich a fluid enters said well, said method including the steps of:providing said'well with a-body of electrolyte; forming a voltaic cellin said electrolyte; moving said voltaic cell in said electrolyte; andmeasuring the voltage produced by said voltaic cell.

9. A method of testing a well to determine the location of any strata atwhich a fluid enters the Well, said method including the steps of:providing said Well with a body of electrolyte; causing iuid to How intosaid Well from the surrounding strata, said fluid changing the strengthof said electrolyte at the point of entrance of said fluid; moving apair of space electrodes through said electrolyte, said electrodes beingof a character to cooperate With adjacent electrolyte to form a voltaiccell; and measuring the potential difference between said electrodes asthey move through said electrolyte.

10. A method of testing a Well to determine the location of any strataat which a fluid enters the Well, said method including the steps of:providing said Well With a body of electrolyte; reducing the hydrostaticpressure in said Well in order to reduce the pressure against the stratasurrounding said Well; moving a pair of space electrodes through saidelectrolyte, said electrodes being of a character to cooperate withadjacent elec-i trolyte to form a voltaic cell; and electrochemicallytesting said electrolyte at various points to determine where it hasbeen diluted,

by fluid entering said well.

In testimony whereof, I hereunto aiiix my signature.

GEORGE H. ENNIS.

